144 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



Pearlsides Maurolicus pennanti (Walbaum) 1792 



Pearlfish 



Jordan and Everman, 1896-1900, P. 577. 



Description. — The presence of an adipose fin be- 

 tween the dorsal and caudal fins, together with 

 luminous organs, distinguishes the pearlsides from 

 all other fishes that occur regularly in the Gulf of 

 Maine. It agrees in both these respects with the 

 lanternfish (p. 143) and with the headlightfish (p. 

 142), but it has a much smaller mouth and a longer 

 adipose fin than the first of these, and it lacks the 

 large luminous patch on the snout that is so strik- 

 ing a feature of the second. Also, the pearlsides, 

 with its herring-like coloration (p. 88) differs strik- 

 ingly from the lanternfish, which has a black back 

 overlaid with silver; and probably the headlight 

 fish as well. 



Figure 62. — Pearlsides (Maurolicus pennanti). After 

 Smitt. 



The pearlsides is a flat-sided, large-headed little 

 fish, its body (about one-fifth as deep as long, ex- 

 cluding caudal fin) deepest forward of the ventral 

 and dorsal fins; its eye very large; its lower jaw pro- 

 jecting; its mouth oblique; and both its jaws armed 

 with minute teeth. The dorsal fin (about 1 1 or 12 

 rays) stands above the space between the ventrals 

 and the anal; the anal is longer than the dorsal. 

 The adipose fin (both of Woods Hole 32 and of 

 Norwegian 33 examples) is low and long, much as it 

 is in the capelin. 34 The caudal fin is broad and 

 slightly forked. 



The pearlsides has been described as without 

 scales, but this is not correct, for both Scandinav- 

 ian and Woods Hole specimens have been found to 

 be clothed with large but extremely thin trans- 

 parent scales. There is no definite lateral line. 



» Sumner, Osburn, and Cole, Bull. U. S. Bur. Fish., vol. 31, Pt. 2, 1913, 

 p. 743. 



" Smltt, Scandinavian Fishes, vol. 1, 1892, p. 933, pi. 44, flg. 3. 



" Ooode and Bean (Smithsonian Contrlb. Knowl., vol. 30, 1895 p. 96) 

 describe It as "very small," but probably their specimens were damaged. 



The most interesting and diagnostic feature of 

 the pearlsides is the presence of a series of lumi- 

 nescent dots situated as follows: 35 First, 12 pairs 

 along the belly between the pectoral and the ven- 

 tral fins, followed by 5 or 6 from the ventral fins to 

 the anal fin, and, after a gap, by 24 or 25 between 

 the center of the anal fin and the base of the caudal 

 fin; all these together form a practically continuous 

 row on each side of the belly from throat to tail. 

 Second, there is a row of larger spots a little higher 

 up on each side, 6 from chin to pectoral fin, and 9 

 thence backward to the ventrals. Third, there is 

 a group of 6 low down on each side of the cheek and 

 throat; there is likewise a spot in front of the base 

 of each pectoral fin and 2 on the chin. 



Color. — The pearlsides is colored much like a 

 herring, with dark bluish or greenish back and lus- 

 trous silvery-white sides and belly. The lumines- 

 cent spots are described as black rimmed, their 

 centers as pale blue in life but turning yellow in 

 alcohol; and there is a narrow black band along the 

 base of the anal fin and from there to the base of 

 the caudal, the latter being barred with a similar 

 black band. 



Size. — Only 1 to 2%. inches long. 



Habits. — The relatives of the pearlsides are oce- 

 anic, living in the mid-depths mostly below 150 

 fathoms, but the pearlsides itself has been found so 

 often in the stomachs of cod and of herring (fish 

 that do not descend to any great depth) that there 

 is no reason to regard it as a "deep-sea" stray, nor 

 has it ever been taken far from land so far as we can 

 learn. It probably spawns in early spring, females 

 with large eggs having been taken in Scottish 

 waters in winter. 



General range. — The pearlsides (there are several 

 other species closely allied to it) ranges widely in 

 the open Atlantic, occurring at times in shoals on 

 the coasts of Norway and in British waters. It is 

 especially common off the coast of Scotland, but 

 has not been recorded often on the American side 

 of the Atlantic. 



Occurrence in the Gulf of Maine. — The known 

 occurrences of the pearlsides in the Gulf have been 

 few. Storer 36 (1867) records one found alive on 

 the beach at Nahant, Mass., in December, 1837; 

 another taken from the stomach of a cod at 



» This account Is based chiefly on Smitt's description and plate, the speci- 

 mens we have seen being In poor condition. 

 « Fishes of Mass., 1887, p. 160, as Scopelus humboldtil. 



